1. Field of the Invention
The present invention relates to a mechanism that gets a gas from a high pressure gas cartridge and that supplies a constant amount of gas per time. This mechanism is effective especially when adopted in such devices as oxygen inhalers or gas burners, in which pulsating of gas is not desirable.
2. Description of the Prior Art
If a surface of a sealing cover of a gas cartridge is flat, a ringlike flat packing has only to be adopted in order to prevent gas leakage when the sealing cover is pierced.
However, if the surface of the sealing cover is not flat as in a calked sealing cover, the neck of the cartridge has to be sealed by an O-ring in addition to the ringlike flat packing. This type of sealing has some demerits. For example, the space between the sealing cover and the packing becomes full of a leaked gas, which exerts a high pressure onto the surface of a sealing cover and presses the O-ring to the periphery of the cartridge. These prevent the cartridge from being moved to a place where the sealing cover can be pierced completely. Therefore, the sealing cover can not be pierced completely, so that lesser amount of gas is supplied as the amount of gas in the cartridge decreases.
A valve pin and a sealing member co-operate to modulate the amount of gas supply. In these devices a gas pressure is not be exerted onto the outer periphery of the sealing member. However, the pressure onto the inner periphery of the sealing member varies while the gas is flowing through the interval between the valve pin and the sealing member, being affected by consumed amount of gas. Therefore, the sealing member is often distorted to vary the interval between the valve pin and the sealing member. Consequently, it is impossible to keep the amount of gas flowing through the interval constant.